Flat panel displays have been used in various products and fields in recent years, and are required to be larger in size, to have higher definition, and to consume less power.
In view of the circumstances, an organic EL display device including an organic EL element which employs electroluminescence (hereinafter, referred to as “EL”) of an organic material draws significant attention as an all-solid flat panel display which is excellent in low voltage driving, rapid response, light emitting property, etc.
The organic EL display device has, for example, an arrangement in which an organic EL element connected to a thin film transistor (TFT) is provided on a substrate made from, for example, a glass substrate providing the TFT thereon.
The organic EL element is a light emitting element capable of emitting light of high luminance by low-voltage direct-current driving, and includes a first electrode, an organic EL layer, and a second electrode which are stacked in this order. Among them, the first electrode is connected to the TFT.
An organic layer, in which a hole injecting layer, a hole transporting layer, an electron blocking layer, a light emitting layer, a hole blocking layer, an electron transporting layer, an electron injecting layer, etc. are stacked, is provided as the organic EL layer between the first electrode and the second electrode.
FIG. 19 is a schematic view illustrating an array of sub pixels of each pixel in a general full-color organic EL display device.
As illustrated in FIG. 19, the full-color organic EL display device is generally formed such that an organic EL element including a light emitting layer of R (red), an organic EL element including a light emitting layer of G (green), and an organic EL element including a light emitting layer of B (blue) are arrayed as sub pixels on a semiconductor substrate for display, such as a TFT substrate, and the full-color organic EL display device displays an image with use of the TFT by selectively causing the organic EL elements to emit light of desired luminance.
In production of such an organic EL display device, at least light emitting layers, made from an organic light emitting material which emits light of colors, are subjected to patterning for respective organic EL elements which are light emitting elements (see, e.g., Patent Literatures 1 and 2).
The organic EL elements are formed by stacking organic films by vapor-deposition, whereas the light emitting layers need to be vapor-deposited on sub pixels of each color.
For example, in a case of a low-molecular kind organic EL display (OLED), an organic film (organic layer) has been conventionally formed in different colors by a vapor-deposition method with use of a vapor-deposition mask.
As a method of forming a pattern on a light emitting layer, for example, there is known a vacuum vapor-deposition method with use of a vapor-deposition mask called “shadow mask”. The vacuum vapor-deposition method is roughly divided into two methods: a method of forming a film while contacting a film formation substrate and a vapor-deposition mask with each other; and a scanning vapor-deposition method of forming a film while separating a film formation substrate and a vapor-deposition mask.
In the vacuum vapor-deposition method with use of a vapor-deposition mask as described above, a film formation substrate and a vapor-deposition source are subjected to patterning in such a way that (i) the substrate and the vapor-deposition source are located to be opposite to each other, (ii) an opening is made in the mask to correspond to a part of a pattern to be formed on a vapor-deposited region in order to prevent vapor-deposition particles from adhering to a region other than the part of the vapor-deposited region, and (iii) vapor-depositing the vapor-deposition particles on the substrate via the opening.